U.S. patent application number 14/254508 was filed with the patent office on 2015-10-22 for electro-mechanical drive system.
This patent application is currently assigned to GM GLOBAL TECHNOLOGY OPERATIONS LLC. The applicant listed for this patent is GM GLOBAL TECHNOLOGY OPERATIONS LLC. Invention is credited to Norman Schoenek, Shawn H. Swales, Goro Tamai.
Application Number | 20150300461 14/254508 |
Document ID | / |
Family ID | 54250022 |
Filed Date | 2015-10-22 |
United States Patent
Application |
20150300461 |
Kind Code |
A1 |
Tamai; Goro ; et
al. |
October 22, 2015 |
ELECTRO-MECHANICAL DRIVE SYSTEM
Abstract
An electro mechanical-drive system includes a main shaft, a
plurality of ball bearings disposed around the main shaft, and a
plurality of roller bearing disposed around the main shaft. At
least one of the ball bearings is aligned with at least one of the
roller bearings along an axis perpendicular to the main shaft. The
ball and roller bearings may support other components of the
electro-mechanical drive system and may be arranged in a nested or
staggered configuration.
Inventors: |
Tamai; Goro; (Bloomfield
Hills, MI) ; Swales; Shawn H.; (Canton, MI) ;
Schoenek; Norman; (Novi, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GM GLOBAL TECHNOLOGY OPERATIONS LLC |
Detroit |
MI |
US |
|
|
Assignee: |
GM GLOBAL TECHNOLOGY OPERATIONS
LLC
Detroit
MI
|
Family ID: |
54250022 |
Appl. No.: |
14/254508 |
Filed: |
April 16, 2014 |
Current U.S.
Class: |
475/5 ;
180/65.25; 903/917 |
Current CPC
Class: |
B60K 6/365 20130101;
F16H 57/0482 20130101; F16H 57/021 20130101; Y02T 10/62 20130101;
Y10S 903/917 20130101; F16H 3/727 20130101; Y02T 10/6239 20130101;
B60K 6/445 20130101; B60K 6/40 20130101; F16H 2200/2007
20130101 |
International
Class: |
F16H 3/72 20060101
F16H003/72; F16H 57/021 20060101 F16H057/021; F16H 3/66 20060101
F16H003/66 |
Claims
1. An electro-mechanical drive system, comprising: a stationary
member; an input member extending along a first axis; a compound
planetary gear arrangement operatively coupled to the input member
such that torque is transmitted from the input member to the
compound planetary gear arrangement; a first electric
motor-generator operatively coupled to the compound planetary gear
arrangement such that torque is transmitted between the first
electric motor-generator and the compound planetary gear
arrangement; a second electric motor-generator operatively coupled
to the compound planetary gear arrangement such that torque is
transmitted between the first electric motor-generator and the
compound planetary gear arrangement; a transfer gear set extending
along a second axis, wherein the transfer gear set is operatively
coupled between the second motor-generator and the compound
planetary gear arrangement such that torque is transmitted between
the second motor-generator and the compound planetary gear
arrangement through the transfer gear set; a plurality of bearings
including: a ball bearing supporting the input member, wherein the
ball bearing is fixed to the stationary member such that the ball
bearing remains constrained relative to the stationary member; and
a roller bearing supporting the input member; and wherein at least
two of the plurality of bearings are aligned with each other along
a third axis, and the third axis is perpendicular to the first
axis.
2. The electro-mechanical drive system of claim 1, wherein the ball
bearing is a first ball bearing, and the electro-mechanical drive
system further comprises a second, third, and fourth ball bearings
disposed around the input member such that the second, third and
four ball bearings jointly support axial and radial loads on the
input member along a first axial direction, a second axial
direction opposite the first axial direction, and a radial
direction perpendicular to the first and second axial
directions.
3. The electro-mechanical drive system of claim 2, wherein the
roller bearing is a first roller bearing, and the
electro-mechanical drive system further comprises a second roller
bearing disposed around the input member such that the second
roller bearing supports radial loads on the input member.
4. The electro-mechanical drive system of claim 3, wherein the
first electric motor-generator includes a rotor shaft extending
along the first axis, and electro-mechanical drive system further
comprises a fifth ball bearing disposed around the rotor shaft such
that the fifth ball bearing supports axial and radial loads on the
rotor shaft.
5. The electro-mechanical drive system of claim 4, wherein the
fifth ball bearing is fixed to the stationary member such that the
fifth ball bearing remains constrained relative to the stationary
member along the first axial direction, the second axial direction,
and the radial direction.
6. The electro-mechanical drive system of claim 5, further
comprising a third roller bearing disposed around the rotor shaft
such that the third roller bearings supports radial loads on the
rotor shaft.
7. The electro-mechanical drive system of claim 6, wherein the
first ball bearing is aligned with the fourth ball bearing along
the third axis.
8. The electro-mechanical drive system of claim 7, wherein the
second roller bearing is aligned with the third ball bearing along
a fourth axis, and the fourth axis is perpendicular to the first
axis.
9. The electro-mechanical drive system of claim 8, wherein the
second ball bearing is aligned with the third roller bearing along
a fifth axis, and the fifth axis is perpendicular to the first
axis.
10. The electro-mechanical drive system of claim 9, wherein the
transfer gear set includes a transfer shaft extending along the
second axis, and the electro-mechanical drive system further
includes a fourth roller bearing disposed around the transfer shaft
such that the fourth roller bearing supports radial loads on the
transfer shaft.
11. The electro-mechanical drive system of claim 10, further
comprising an sixth ball bearing disposed around the transfer
shaft, wherein the sixth ball bearing is fixed to the stationary
member such that the sixth ball bearing remains constrained
relative to the stationary member along the first axial direction,
the second axial direction, and the radial direction.
12. The electro-mechanical drive system of claim 11, wherein the
rotor shaft is a first rotor shaft, and the second electric motor
generator includes a second rotor shaft extending along a sixth
axis, and the sixth axis is parallel to the first and second
axes.
13. The electro-mechanical drive system of claim 12, wherein
further comprising a seventh ball bearing disposed around the
transfer shaft.
14. The electro-mechanical drive system of claim 13, wherein the
seventh ball bearing is aligned with the fourth ball bearing along
the third axis.
15. The electro-mechanical drive system of claim 13, wherein the
seventh ball bearing overlaps the fourth roller bearing along the
radial direction such that a seventh axis intersects the fourth
roller bearing and the seventh ball bearing, and the seventh axis
is perpendicular to the first axis.
16. An electro-mechanical drive system, comprising: a main shaft; a
plurality of ball bearings disposed around the main shaft; a
plurality of roller bearings disposed around the main shaft;
wherein at least two of the ball bearings are aligned along an axis
perpendicular to the main shaft.
17. The electro-mechanical drive system of claim 16, further
comprising a stationary member, wherein the plurality of ball
bearings includes a first ball bearing supporting the main shaft,
and the first ball bearing is fixed to the stationary member such
that the first bearing remains constrained relative to the
stationary member along a first axial direction, a second axial
direction opposite the first axial direction, and a radial
direction.
18. The electro-mechanical drive system of claim 17, wherein the
plurality of roller bearings includes a first roller bearing
supporting the main shaft along the radial direction, and the first
roller bearing is spaced apart from the first ball bearing along
the first axial direction.
19. An electro-mechanical drive system, comprising: a main shaft; a
plurality of ball bearings disposed around the main shaft; a
plurality of roller bearings disposed around the main shaft; and
wherein at least one of the ball bearings is aligned with at least
one of the roller bearings along an axis perpendicular to the main
shaft.
20. The electro-mechanical drive system of claim 19, further
comprising a stationary member, wherein the plurality of ball
bearings includes a first ball bearing supporting the main shaft,
and the first ball bearing is fixed to the stationary member such
that the first bearing remains constrained relative to the
stationary member along a first axial direction, a second axial
direction opposite the first axial direction, and a radial
direction, the plurality of roller bearings includes a first roller
bearing supporting the main shaft along the radial direction, and
the first roller bearing is spaced apart from the first ball
bearing along the first axial direction.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to an electro-mechanical
drive system.
BACKGROUND
[0002] Electro-mechanical drive systems may be part of a hybrid
powertrain and includes at least one electric motor-generator
capable of converting electrical energy into kinetic energy. In
addition, the electro-mechanical drive system can receive power
from an internal combustion engine. The internal combustion engine
combusts fuel to generate torque.
SUMMARY
[0003] It is useful to minimize the mechanical losses in an
electro-mechanical drive system in order to minimize fuel
consumption of the hybrid powertrain. It is also useful to minimize
the space occupied by the electro-mechanical drive system. To do
so, the bearings in the electro-mechanical drive system may be
arranged as described in the present disclosure. In an embodiment,
the electro-mechanical drive system includes a stationary member,
an input member extending along a first axis, and a compound
planetary gear arrangement operatively coupled to the input member.
Torque can be transmitted from the input member to the compound
planetary gear arrangement. The electro-mechanical drive system
further includes first and second electric motor-generators
operatively coupled to the compound planetary gear arrangement.
Torque can be transmitted between the first electric
motor-generator and the compound planetary gear arrangement.
Moreover, torque can be transmitted between the first electric
motor-generator and the compound planetary gear arrangement. The
electro-mechanical drive system additionally includes a transfer
gear set extending along a second axis. The transfer gear set is
operatively coupled between the second motor-generator and the
compound planetary gear arrangement. Accordingly, torque can be
transmitted between the second motor-generator and the compound
planetary gear arrangement through the transfer gear set. In
addition, the electro-mechanical drive system includes a plurality
of bearings. For instance, the electro-mechanical drive system
includes at least one ball bearing and at least one roller bearing.
The ball bearing supports the input member and is fixed to the
stationary member such that the ball bearing remains constrained
relative to the stationary member. The roller bearing supports the
input member. At least two of the bearings are aligned with each
other along a third axis. The third axis is perpendicular to the
first axis. In another embodiment, at least two of the ball
bearings are aligned along an axis perpendicular to the input
member, which may be a main shaft. In another example, at least one
of the ball bearings is aligned with at least one of the roller
bearings along an axis perpendicular to the input member (e.g.,
main shaft).
[0004] The above features and advantages and other features and
advantages of the present invention are readily apparent from the
following detailed description of the best modes for carrying out
the invention when taken in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a schematic, side, sectional view of a hybrid
powertrain of a vehicle, wherein the hybrid powertrain includes an
electro-mechanical drive system;
[0006] FIG. 2 is a schematic, side, sectional view of part of the
electro-mechanical drive system;
[0007] FIG. 3 is a schematic, side, sectional view of another part
of the electro-mechanical drive system shown in FIG. 2; and
[0008] FIG. 4 is schematic, side, sectional view of an
electro-mechanical drive system in accordance with another
embodiment of the present disclosure.
DETAILED DESCRIPTION
[0009] Referring to the drawings in which like elements are
identified with identical numerals throughout, FIG. 1 schematically
illustrates a hybrid powertrain 12 of a vehicle 10. In other words,
the vehicle 10 includes the hybrid powertrain 12, which is capable
of propelling the vehicle 10. The hybrid powertrain 12 includes an
internal combustion engine 14 and an electro-mechanical drive
system 16 operatively coupled to the internal combustion engine 14.
Accordingly, the internal combustion engine 14 can transmit torque
to the electro-mechanical drive system 16. The electro-mechanical
drive system 16 includes a final drive unit 18 and an electrically
variable transmission (EVT) 20 operatively coupled to the final
drive unit 18. As such, the final drive unit 18 can receive torque
from the EVT 20. The final drive unit 18 includes a differential
22, which in turn has a differential ring gear 24 operatively
coupled to the EVT 20. As a result, the EVT 20 can transmit torque
to the differential ring gear 24 of the differential 22.
[0010] With reference to FIG. 1, the EVT 20 includes an input
member 26, such as a main shaft 27, operatively coupled to the
internal combustion engine 14. Consequently, the internal
combustion engine 14 can transmit torque to the input member 26. In
other words, the internal combustion engine 14 can transmit torque
to the EVT 20 via the input member 26. The input member 26 extends
along a first axis A. The input member 26 may have a substantially
cylindrical shape and can rotate about the first axis A upon
receipt of torque from the internal combustion engine 16.
[0011] The EVT 20 further includes a stationary member 28 at least
partially encasing the input member 26. As a non-limiting example,
the stationary member 28 may be configured as a case 30 or housing.
Regardless of its configuration, the stationary member 28 remains
stationary while the input member 26 rotates about the first axis
A. To this end, the stationary member 28 may be fixed to the
vehicle body of the vehicle 10. Accordingly, the stationary member
28 (e.g., case 30) remains constrained or substantially stationary
relative to the vehicle body of the vehicle 10.
[0012] The EVT 20 additionally includes a compound planetary gear
arrangement 32 operatively coupled to the input member 26.
Accordingly, torque can be transmitted from the input member 26 to
the compound planetary gear arrangement 32. The compound planetary
gear arrangement 32 includes a first planetary gear set 34 and a
second planetary gear set 36. The first planetary gear set 34 is
operatively coupled to the input member 26. Consequently, torque
can be transmitted from the input member 26 to the first planetary
gear set 34. The second planetary gear set 36 is operatively
coupled to the first planetary gear set 34. As a result, torque can
be transmitted from the first planetary gear set 34 to the second
planetary gear set 36.
[0013] The electro-mechanical drive system 16 further includes a
first electric motor-generator 38 is operatively coupled to the
compound planetary gear arrangement 32. Accordingly, torque can be
transmitted between the first electric motor-generator 38 and the
compound planetary gear arrangement 32. Specifically, the first
electric motor-generator 38 is operatively coupled to the second
planetary gear set 36. Because the first electric motor-generator
38 is operatively coupled to the second planetary gear set 36,
torque can be transmitted from the first electric motor-generator
38 to the second planetary gear set 36 (or another component of the
EVT 20). The first electric motor-generator 38 is electrically
connected to an energy storage device, such as a battery pack, and
can operate in motoring mode and generating mode. In the motoring
mode, the first electric motor-generator 38 can convert electrical
energy received from the energy storage device into mechanical
energy (e.g., torque). Conversely, when operating in the generating
mode, the first electric motor-generator 38 coverts mechanical
energy (e.g., torque) into electrical energy. The electrical energy
generated by the electric motor-generator 38 can then be
transmitted to the energy storage device. The first electric
motor-generator 38 includes a first rotor shaft 40 extending along
the first axis A. The electro-mechanical drive system 16 further
includes an input extension member 42 (FIG. 2) extending through
the first rotor shaft 40 along the first axis A. The input
extension member 42 (FIG. 2) is operatively coupled to the input
member 26 and can therefore rotate about the first axis A
simultaneously with the input member 26. In other words, the input
extension member 42 can rotate about the first axis A upon receipt
of the torque from the input member 26. The input member 26 and the
input extension member 42 (FIG. 2) may be collectively referred to
as an input member assembly 44.
[0014] The EVT 20 also includes a transfer gear set 46 capable of
receiving torque from the input member 26 through the compound
planetary gear arrangement 32. Specifically, the transfer gear set
46 is operatively coupled to the second planetary gear set 36.
Accordingly, torque can be transmitted from the second planetary
gear set 36 to the transfer gear set 46. In the depicted
embodiment, the transfer gear set 46 is a coaxial transfer gear set
46 and extends along a second axis B. The second axis B is offset
relative to the first axis A. As a non-limiting example, the second
axis B is parallel to the first axis A. In the depicted embodiment,
the second axis B is spaced apart from the first axis along a
radial direction R.
[0015] The electro-mechanical drive system 16 further includes a
second electric motor-generator 48 operatively coupled to the
transfer gear set 46. As a consequence, the toque can be
transmitted from the second electric motor-generator 48 to the
transfer gear set 46. The transfer gear set 46 is also operatively
coupled to the first planetary gear set 34. Accordingly, torque can
be transmitted from the transfer gear set 46 to the first planetary
gear set 36. In particular, torque can be transmitted from the
second electric motor-generator 48 to the first planetary gear set
34 through the transfer gear set 46. The second electric
motor-generator 48 includes a second rotor shaft 50 operatively
coupled to the transfer gear set 46. As a result, torque can be
transmitted from the second rotor shaft 50 to the transfer gear set
46. The transfer gear set 46 is also operatively coupled to the
final drive unit 18. Thus, torque can be transmitted from the
transfer gear set 46 to the final drive unit 18. In particular, the
transfer gear set 46 is operatively coupled to the differential 22.
In the depicted embodiment, the transfer gear set 46 is operatively
coupled to the differential ring gear 24 of the differential 22.
Accordingly, torque can be transmitted from the transfer gear set
46 to the differential 22 via the differential ring gear 24. The
second electric motor-generator 48 is operatively coupled to the
compound planetary gear arrangement 32 through the transfer gear
set 46. In other words, the transfer gear set 46 is operatively
coupled between the second electric motor-generator 48. As such,
torque can be transmitted between the second electric
motor-generator 48 and the compound planetary gear arrangement 32
through the transfer gear set 46.
[0016] The electro-mechanical drive system 16 includes a plurality
of bearings 19. In particular, the electro-mechanical drive system
16 includes a plurality of ball bearings 11, such as deep groove
ball bearings, and a plurality of roller bearings 13, such as
needle roller bearings, as discussed in detail below. Each roller
bearing 13 includes a plurality of rollers along its circumference.
At least some of the ball bearings 11 are disposed around the input
member 26 (e.g., main shaft 27). At least some of the roller
bearings 13 are disposed around the input member 26 (e.g., main
shaft 27). As discussed in detail below, at least two bearings 19
are aligned with each other along an axis (see, e.g. axes C, D, and
E in FIG. 2) that is perpendicular (or substantially perpendicular)
to the first axis A. For example, at least one of the ball bearings
11 may be aligned with at least one of the roller bearings 13 along
an axis (see, e.g. axes C, D, and E in FIG. 2) that is
perpendicular to the input member 26 (e.g. main shaft 27). Also, at
least two ball bearings 11 are aligned with each other along an
axis (see, e.g. axes C, D, and E in FIG. 2) that is perpendicular
(or substantially perpendicular) to the first axis A and the input
member 26 (e.g., main shaft 27).
[0017] With reference to FIG. 2, the input member 26 defines a
first input end 52 and a second input end 54 opposite the first
input end 52. The first input end 52 is directly coupled to the
internal combustion engine 14 (FIG. 1), and the second input end 54
is directly coupled to the input extension member 42. The second
input end 54 is spaced apart from the first input end 54 along a
first axial direction X1. The first axial direction X1 is
perpendicular to the radial direction R. In the present disclosure,
a second axial direction X2 is defined as the direction opposite to
the first direction X1. The first rotor shaft 40 is at least
partially disposed over the input extension member 42 and input
member 26.
[0018] As discussed above, the EVT 20 includes the first and second
planetary gear sets 34, 36. In the depicted embodiment, the first
planetary gear set 34 includes a first sun gear 74 and a plurality
of first planet gears 76 disposed around the first sun gear 74. The
first sun gear 74 is disposed around the input member 26.
Specifically, the first sun gear 74 is operatively coupled to the
input member 26 and, accordingly, torque can be transmitted from
the input member 26 to the first sun gear 74. Upon receipt of
torque from the input member 26, the first sun gear 74 rotates
about the first axis A. Further, the first sun gear 74 continuously
meshes with the first planet gears 76. As a result, the rotation of
the first sun gear 74 causes the first planet gears 76 to rotate
around the first sun gear 74. The first planetary gear set 34
further includes a first carrier 78 coupling all the first planet
gears 76 to one another. In addition to the first carrier 78, the
first planetary gear set 34 includes a first internal ring gear 80
continuously meshing with the first planet gears 76. Consequently,
the rotation of the first plant gears 76 about the first axis A
causes the first internal ring gear 80 to rotate about the first
axis A. The first planetary gear set 34 further includes a first
external ring gear 84 connected to the first internal ring gear 80.
Accordingly, the rotation of the first internal ring gear 80 about
the first axis A causes the first external ring gear 84 to rotate
about the first axis A. The first internal ring gear 80 may be
integrally formed with the first external ring gear 84 so as to
form a one-piece structure. The first external ring gear 84 is
operatively coupled to the transfer gear set 46 such that torque
can be transmitted between the transfer gear set 46 and the first
external ring gear 84.
[0019] The second planetary gear set 36 includes a second sun gear
86 and a plurality of second planet gears 88 disposed around the
second sun gear 86. The second sun gear 86 is disposed around the
first rotor shaft 40. Specifically, the second sun gear 86 is
operatively coupled to the first rotor shaft 40 and, accordingly,
torque can be transmitted from the first rotor shaft 40 to the
second sun gear 86. Upon receipt of torque from the first rotor
shaft 40, the second sun gear 86 rotates about the first axis A.
Further, the second sun gear 86 continuously meshes with the second
planet gears 88. As a result, the rotation of the second sun gear
86 about the first axis A causes the second planet gears 88 to
rotate around the second sun gear 86. The second planetary gear set
36 further includes a second carrier 90 coupling all the second
planet gears 88 to one another. In addition to the second carrier
90, the second planetary gear set 36 includes a second internal
ring gear 92 continuously meshing with the second planet gears 88.
Consequently, the rotation of the second plant gears 88 about the
first axis A causes the second internal ring gear 92 to rotate
about the first axis A. The second planetary gear set 36 further
includes a second external ring gear 96 connected to the first
internal ring gear 92. Accordingly, the rotation of the second
internal ring gear 92 about the first axis A causes the second
external ring gear 96 to rotate about the first axis A. The first
internal ring gear 92 may be integrally formed with the second
external ring gear 96 to form a one-piece structure. The second
external ring gear 96 is operatively coupled to the transfer gear
set 46 such that torque can be transmitted between the transfer
gear set 46 and the second external ring gear 96.
[0020] The EVT 20 includes a first fixed, free bearing arrangement
56 for supporting axial and radial loads on the input member 26. As
used herein, the term "fixed, free bearing arrangement" refers to a
group of bearing coupled a component of the EVT 20, such as the
input member 26, in order to support axial and radial loads acting
on the that component (e.g., input member 26). Specifically, the
term "fixed, free bearing arrangement" refers to a plurality of
bearings, wherein one or more bearings support the axial and radial
loads acting on a component (e.g., input member 26) and another
bearing (or group of bearings) only support the radial loads acting
on that component. In other words, in a fixed, free bearing
arrangement, at least one bearing 19 (or group of bearings 19) is
constrained or substantially stationary along the radial direction
R as well as the first and second axial directions X1, X2, and at
least one other bearing 19 (or group of bearings) is constrained or
substantially stationary along the radial direction R but is free
to move along the first and second axial directions X1, X2. A
fixed, free bearing arrangement including only two bearings may be
referred to as a fixed, free bearing pair. The fixed, free bearing
arrangements in the EVT 20 help minimize mechanical losses by
minimizing the effective bearing mean diameters of the
bearings.
[0021] The first fixed, free bearing arrangement 56 includes a
first ball bearing 58, such as a deep groove ball bearing,
supporting the input member 26 and a first roller bearing 62, such
as a needle roller bearing, supporting the input member 26. The
first ball bearing 58 and the first roller bearing 62 are part of
the plurality of bearings 19 (FIG. 1). In the depicted embodiment,
each ball bearing 11, such as the first ball bearing 58, includes
an inner race 64, outer race 66, and a plurality of balls 68. The
inner and outer races 64, 66 have a substantially annular shape and
are spaced apart from each other so as to define an annular groove,
which is configured, shaped, and sized to receive the balls 68. The
first ball bearing 58 is disposed around the input member 26 and is
therefore coaxially arranged relative to the input member 26. The
first ball bearing 58 is fixed to the stationary member 28 (e.g.,
case 30) along the radial direction R and the axial direction
(e.g., the first axial direction X1, the second axial direction X2,
or both). In the depicted embodiment, the first ball bearing 58 is
fixed to the stationary member 28 along the radial direction R, the
first axial direction X1, and the second axial direction X2. Thus,
the first ball bearing 58 remains constrained or substantially
stationary relative to the stationary member 28 along the radial
direction R, the first axial direction X1, and the second axial
direction X2. A snap ring 70 may be coupled to the stationary
member 28 in order to fix the first ball bearing 58 along the first
axial direction X1. A flange 72 of the stationary member 28 abuts
the first ball bearing 58 in order to fix the first ball bearing 58
along the second axial direction X2. The first ball bearing 58 is
closer to the first input end 52 than the first roller bearing
62.
[0022] As discussed above, the first fixed, free bearing
arrangement 56 also includes the first roller bearing 62, such as a
needle roller bearing, supporting the input member 26. Each roller
bearing 13, such as the first roller bearing 62, includes an
annular body and roller disposed along the circumference of the
annular body. Specifically, the first roller bearing 62 contacts
the input member 26 and the first rotor shaft 40 and only supports
radial loads acting on the input member 26 (or any member of the
EVT 20 supported by the first roller bearing 62. Accordingly, the
first roller bearing 62 does not support axial loads acting on the
input member 26. Accordingly, the first roller bearing 62 is
axially free. In the depicted embodiment, the first roller bearing
62 is disposed around the input member 26 and is arranged coaxially
relative to the input member 26. Specifically, the first roller
bearing 62 contacts the input member 26 and is disposed between the
input member 26 and the first rotor shaft 40. The first roller
bearing 62 is closer to the second input end 54 than the first ball
bearing 58. Moreover, the first roller bearing 62 is spaced apart
from the first ball bearing 58 along the first axial direction X1.
Further, the first roller bearing 62 can remain constrained or
substantially stationary relative to the stationary member 28 along
the radial direction R.
[0023] As discussed above, the first fixed, free bearing
arrangement 56 supports axial and radial loads acting on the input
member 26 (or any member of the EVT 20 supported by the first
fixed, free bearing arrangement 56). In the present disclosure, the
term "axial load" refers to forces acting on a component of the EVT
20, such as the input member 26, in the first axial direction X1 or
the second axial direction X2. The term "radial load" refers to
forces acting on a component of the EVT 20, such as the input
member 26, in the radial direction R. In addition, the term "radial
load" may include forces acting on a component of the EVT 20 (e.g.,
input member 26) along a direction obliquely angled to the first
axial direction X1 and the second axial direction X2.
[0024] The EVT 20 includes a second fixed, free bearing arrangement
82 supporting the first internal ring gear 80, the first external
ring gear 84, the second internal ring gear 92, and the second
external ring gear 96. In the depicted embodiment, the second
fixed, free bearing arrangement 82 includes a second ball bearing
94 fixed to the stationary member 28 along the first axial
direction X1. Consequently, the second ball bearing 94 remains
constrained or substantially stationary relative to the stationary
member 28 along the first axial direction X1. The second ball
bearing 94 is disposed around the input member 26. In particular, a
center support 98 of the stationary member 28 can contact the
second ball bearing 94 in order to prevent the second ball bearing
94 from moving in the first axial direction X1. However, the center
support 98 does not restrict the movement of the second ball
bearing 94 in the second axial direction X2.
[0025] The second fixed, free bearing arrangement 82 also includes
a third ball bearing 102 disposed around the input member 26. The
EVT 20 includes a hub 104 supporting the third ball bearing 102.
The hub 104 is disposed entirely within the stationary member 28
and interconnects the second internal ring gear 92 and the first
carrier 78. Because the second internal ring gear 92 is directly
connected to the second external ring gear 96, the hub 104
interconnects the second external ring gear 96 with the first
carrier 78. Moreover, the hub 104 is coaxially arranged relative to
the input member 26 and is disposed between a second roller bearing
106 and the third ball bearing 102. When the input member 26 is
subjected to a force in the first axial direction X, the force is
transferred from the third ball bearing 102 to the second ball
bearing 94 via the hub 104 and the second internal ring gear 92.
Because the second ball bearing 94 is fixed to the stationary
member 28 along the first axial direction X1, the third ball
bearing 102 is fixed to the stationary member 28 along the axial
direction X1 via the second ball bearing 94. Accordingly, the third
ball bearing 102 can support axial loads acting on the input member
26 (or any member of the EVT 20 supported by the third ball bearing
102) in the first axial direction X1. In other words, the third
ball bearing 102 is operatively coupled to the second ball bearing
94 such that an axial load on the input member 26 in the first
axial direction X1 can be transferred from the third ball bearing
104 to the second ball bearing 94. In addition to axial loads, the
third ball bearing 102 can support radial loads acting on the input
member 26 (or any member of the EVT 20 supported by the third ball
bearing 102). Furthermore, the third ball bearing 102 is disposed
between the hub 104 and a web 112 supporting the first internal
ring gear 80. The third ball bearing 102 is therefore operatively
coupled between the first internal ring gear 80 and the second
internal ring gear 92.
[0026] The second fixed, free bearing arrangement 82 further
includes fourth ball bearing 108 fixed to the stationary member 28
in the second axial direction X2 such that the fourth bearing 108
remains constrained or substantially stationary relative to the
stationary member 28 along the second axial direction X2. The
fourth ball bearing 108 is disposed around the input member 26. The
stationary member 28 includes a cover 110 contacting and supporting
the fourth ball bearing 108 in order to fix the fourth ball bearing
108 to the stationary member 28 in the second axial direction X2
and the radial direction R. The cover 100 may include a cover
flange 101 for supporting the fourth ball bearing 108 in the radial
direction R. Thus, the fourth ball bearing 108 is fixed to the
stationary member 28 along the second axial direction X and the
radial direction R such that the fourth ball bearing 108 remains
constrained or substantially stationary relative to the stationary
member 28 along the second axial direction X2 and the radial
direction R. The fourth ball bearing 108 is disposed around the
input member 26 and adjacent the first carrier 78. The EVT 20
includes a ring support 114 supporting the first external ring gear
84. The fourth ball bearing 108 is disposed between the cover
flange 101 and the ring support 114. Further, the fourth ball
bearing 108 is closer to the first input end 52 than the second
ball bearing 94 and the third ball bearing 102. The third ball
bearing 102 is closer to the second input end 54 than the second
ball bearing 94 and the fourth ball bearing 108. The third ball
bearing 102 is axially disposed between the second ball bearing 94
and the fourth ball bearing 108. Moreover, the third ball bearing
102 is operatively coupled between the first and planetary gear
sets 34, 36.
[0027] When the second internal ring gear 92 is subjected to a
force in the second axial direction X2, the force is transferred
from the second ball bearing 94 to the fourth ball bearing 108
through the second internal ring gear 92, the hub 104, the third
ball bearing 102, web 112, the first internal ring gear 80, the
first external ring gear 84, and the ring support 114. Because the
fourth ball bearing 108 is fixed to the stationary member 28 along
the second axial direction X, the second internal ring gear 92
remains constrained or substantially stationary relative to the
stationary member 28 along the second axial direction X when the
second internal ring gear 92 is subjected to a force in the second
axial direction X2. Therefore, the second ball bearing 94, the
third ball bearing 102, and the fourth ball bearing 108 jointly fix
the second internal ring gear 92 along the second axial direction
X2. Further, the second ball bearing 94, the third ball bearing
102, and the fourth ball bearing 108 also jointly fix the second
internal ring gear 92 along the first axial direction X1.
Specifically, when the second internal ring gear 92 is subjected to
a force in the first axial direction X1, force is transferred from
the fourth ball bearing 108 to the second ball bearing 94 through
ring support 114, the first external ring gear 84, the first
internal ring gear 80, the web 112, the third ball bearing 102, the
hub 104, and the second internal ring gear 92. Because the second
ball bearing 94 is fixed to the stationary member 28 in the first
axial direction X1, the second internal ring gear 92 remains
constrained or substantially stationary relative to the stationary
member 28 along the first axial direction X1 when the second
internal ring gear 92 is subjected to a force in the first axial
direction X1. Thus, the second ball bearing 94, the third ball
bearing 102, and the fourth ball bearing 108 jointly fix the second
internal ring gear 92 along the first axial direction X1.
[0028] The second fixed, free bearing arrangement 82 also includes
the second roller bearing 106, which only supports radial loads
acting on the input member 26 along the radial direction R (or any
other member of the EVT 20 supported by the second fixed, free
bearing arrangement 82). The second roller bearing 106 may be a
needle roller bearing and is disposed between the input member 26
and the hub 104. Moreover, the second roller bearing 106 is
coaxially arranged relative to the input member 26 and can be in
direct contact with the input member 26 and the hub 104. The second
roller bearing 106 is disposed around the input member 26 and is
not fixed to the stationary member 28 along the first and second
axial directions X1, X2. Rather, the second roller bearing 106
supports the input member 26 only along the radial direction R.
[0029] The EVT 20 additionally includes a third fixed, free bearing
arrangement 116 for supporting the first rotor shaft 40. In the
depicted embodiment, the third fixed, free bearing arrangement 116
includes a fifth ball bearing 118 fixed to the stationary member 28
in the first axial direction X1, second axial direction X2, and
radial direction R. Accordingly, the fifth ball bearing 118 remains
constrained or substantially stationary relative to the stationary
member 28 along first axial direction X1, second axial direction
X2, and radial direction R. As a non-limiting example, snap rings
70 may be fixed to the stationary member 28 to fix the fifth ball
bearing along the first and second axial direction X1, X2. The
stationary member 28 may directly contact the fifth ball bearing
118 in order to fix the fifth ball bearing 118 along the radial
direction R. The fifth ball bearing 118 may be coaxially arranged
relative to the first rotor shaft 40 and may be in direct contact
with the stationary member 28 and the first rotor shaft 40.
Further, the fifth ball bearing 118 is disposed around the first
rotor shaft 40 and supports axial and radial loads on the first
rotor shaft 40.
[0030] The third fixed, free bearing arrangement 116 further
includes a third roller bearing 120 (e.g., needle roller bearing)
supporting the first rotor shaft 40. Specifically, the third roller
bearing 120 is disposed around the first rotor shaft 40 and only
supports radial loads on the first rotor shaft 40. In the depicted
embodiment, the third roller bearing 120 is spaced apart from the
fifth ball bearing 118 along the second axial direction X. Further,
the third roller bearing 120 may be in direct contact with the
first rotor shaft 40 and the center support 98 of the stationary
member 28. As a consequence, the third roller bearing 120 is fixed
to the stationary member 28 only along the radial direction R. As
such, the third roller bearing 120 remains constrained or
substantially stationary relative to the stationary member 28 only
along the radial direction R. In summary, the first, second, and
third fixed, free bearing arrangements 56, 82, 116 in the EVT 20
help minimize mechanical losses by minimizing the effective mean
diameters of the bearings 19.
[0031] At least some of the bearings 19 of the EVT 20 described
above (e.g., the first ball bearing 58) are arranged in a nested or
staggered configuration in order to minimize the length of the
electro-mechanical drive system 16. In the depicted embodiment, the
first ball bearing 58 is substantially aligned with the fourth ball
bearing 108 along a third axis C in order to minimize the length of
the electro-mechanical drive system 16. The third axis C is
perpendicular to the first axis A. Thus, the third axis C is
perpendicular to the input member 26 (e.g., main shaft 27). The
third ball bearing 102 is substantially aligned with the second
roller bearing 106 along a fourth axis D in order to minimize the
length of the electro-mechanical drive system 16. The fourth axis D
is perpendicular to the first axis A. Thus, the fourth axis D is
perpendicular to the input member 26 (e.g., main shaft 27). The
second ball bearing 94 is substantially aligned with the third
roller bearing 120 along a fifth axis E in order to minimize the
length of the electro-mechanical drive system 16. The fifth axis E
is perpendicular to the first axis A. Therefore, the fifth axis E
is perpendicular to the input member 26 (e.g., main shaft 27).
[0032] With reference to FIG. 3, the transfer gear set 46 extends
along a second axis B and is operatively coupled to the compound
planetary gear arrangement 32 (FIG. 1). The transfer gear set 46
includes a transfer shaft 122 extending along the second axis B.
The second axis B is offset but parallel to the first axis A. The
transfer shaft 122 can rotate about the second axis B and defines a
first shaft end 123 and a second shaft end 125 opposite the first
shaft end 123. In addition to the transfer shaft 122, the transfer
gear set 46 includes a first transfer gear 124, a second transfer
gear 126, and a third transfer gear 128 spaced apart from one
another along the second axis B. Each of the first transfer gear
124, second transfer gear 126, and third transfer gear 128 can
rotate about the second axis B and is disposed round the transfer
shaft 122. The first transfer gear 124 is operatively coupled to
the second motor 48. Specifically, the first transfer gear 124 is
operatively coupled to the second motor 48 such that rotation of
the second rotor shaft 50 causes first transfer gear 124 to rotate
about the second axis B. In the depicted embodiment, a motor gear
130 is attached to the second rotor shaft 50. Consequently, the
rotation of the second rotor shaft 50 causes the motor gear 130 to
rotate about a sixth axis F. The second rotor shaft 50 extends
along the sixth axis F. The sixth axis F is parallel to the second
axis B and the first axis A. The motor gear 130 meshes with the
first transfer gear 124. Accordingly, the rotation of the motor
gear 130 about the sixth axis F causes the first transfer gear 124
to rotate about the second axis B. In turn, the first transfer gear
124 meshes with the first external ring gear 84 and, consequently,
the rotation of the first transfer gear 124 about the second axis B
causes the first external ring gear 84 to rotate about the first
axis A (FIG. 2). The first transfer gear 124 is not rotatably
coupled to the transfer shaft 122. As such, the transfer shaft 122
can rotate independently of the first transfer gear 124.
[0033] The third transfer gear 128 is operatively coupled to the
second external ring gear 96 such that torque can be transmitted
between the second external ring gear 96 and the transfer gear 128.
Specifically, the third transfer gear 128 meshes with the second
external ring gear 96. As a result, the rotation of the second
external ring gear 96 about the first axis A (FIG. 2) causes the
third transfer gear 128 to rotate bout the second axis B. Further,
the third transfer gear 128 is rotatably coupled to the transfer
shaft 122. Therefore, the rotation of the third transfer gear 128
about the second axis B causes the transfer shaft 122 to rotate
about the second axis B. Moreover, the rotation of the transfer
shaft 122 about the second axis B causes the second transfer gear
126 to rotate about the second axis B.
[0034] The second transfer gear 126 is operatively coupled to the
differential 22 (FIG. 1). As such, torque can be transmitted from
the second transfer gear 126 to the differential 22. In particular,
the second transfer gear 126 meshes with the differential ring gear
24, thereby allowing torque to be transmitted from the second
transfer gear 12 to the differential ring gear 24.
[0035] The electro-mechanical drive system 16 further includes a
fourth fixed, free bearing arrangement 132 for supporting the
transfer shaft 122. The fourth fixed, free bearing arrangement 132
supports axial and radial loads acting on the transfer shaft 122
(or any other member of the EVT 20 supported by the fourth fixed,
free bearing arrangement 132) and helps minimize mechanical losses
in the electro-mechanical drive system 16. In the depicted
embodiment, the fourth fixed, free bearing arrangement 132 includes
a sixth ball bearing 134 disposed around the third transfer gear
128 and the transfer shaft 122. The sixth ball bearing 134 is
closer to the second shaft end 125 than to the first shaft end 123.
The center support 98 of the stationary member 28 contacts the
sixth ball bearing 134, thereby fixing the sixth ball bearing 134
to the stationary member 28 along the first axial direction X1, the
second axial direction X2, and the radial direction R. Accordingly,
the sixth ball bearing 134 remains constrained or substantially
stationary relative to the stationary member 28 (e.g., case) in the
first axial direction X1, the second axial direction X2, and the
radial direction R.
[0036] The fourth fixed, free bearing arrangement 132 further
includes a fourth roller bearing 136 disposed around the transfer
shaft 122. The fourth roller bearing 134 supports radial loads on
the transfer shaft 122 and is closer to the first shaft end 123
than the second shaft end 125. Moreover, the fourth roller bearing
134 only supports the transfer shaft 122 along the radial direction
R. To do so, the fourth roller bearing 134 is fixed to the
stationary member 28 along the radial direction R. Accordingly, the
fourth roller bearing 134 remains constrained or substantially
stationary relative to the stationary member 28 along the radial
direction R. Thus, the fourth roller bearing 134 only supports
radial loads on the transfer shaft 122.
[0037] Some of the bearings supporting the transfer shaft 122 are
arranged in a nested or staggered configuration in order to
minimize the length of the electro-mechanical drive system 16. The
EVT 20 includes a seventh ball bearing 138 overlapping the fourth
roller bearing 136 along the radial direction R. The seventh ball
bearing 138 supports the transfer shaft 122 and is disposed around
the transfer shaft 122. In particular, the seventh ball bearing 138
overlaps the fourth roller bearing 136 along the radial direction R
such a seventh axis G, which is perpendicular to the first and
second axes A, B, intersects the fourth roller bearing 136 and the
seventh ball bearing 138. The seventh ball bearing 138 is aligned
with the fourth ball bearing 108 along the third axis C.
[0038] The stationary member 28 (e.g., case 30) entirely or partly
encases the compound planetary gear arrangement 32, the first
electric motor-generator 38, the second electric motor-generator
48, the transfer gear set 46, the plurality of ball bearings 11
(e.g., deep groove ball bearings), and the plurality of roller
bearings 13 (needle roller bearings).
[0039] FIG. 4 schematically illustrates an electro-mechanical drive
system 216 in accordance with another embodiment of the present
disclosure. The structure and operation of the electro-mechanical
drive system 216 is substantially similar or identical to the
electro-mechanical drive system 16, except for the features
described below. In this embodiment, the electro-mechanical drive
system 216 does not include the input extension member 42 (FIG. 2).
Rather, the input member 226 extends all the way through the first
rotor shaft 40 along the first axis A. In the depicted embodiment,
the input member 226 (e.g., main shaft 27) is a one-piece structure
and defines a first input end 252 and a second input end 254
opposite the first input end 252. The second input end 252 is
disposed outside the first electric motor-generator 38.
[0040] With continued reference to FIG. 4, electro-mechanical drive
system 16 further includes a fifth roller bearing 258 and an eighth
ball bearing 270 supporting the input member 226. The fifth roller
bearing 258 replaces the first ball bearing 58 (FIG. 2) and is
disposed in the same location as the first ball bearing 58. Because
the first ball bearing 58 is replaced with the fifth roller bearing
258, the fourth ball bearing 108 of the electro-mechanical drive
system 216 has a smaller mean diameter than the fourth ball bearing
of the electro-mechanical drive system 16. In this embodiment, the
fourth ball bearing 108 is substantially aligned with the fifth
roller bearing 258 along the third axis C. The fifth roller bearing
258 can support only radial loads on the input member 26 (e.g.,
main shaft 27) and is closer to the first input end 252 than the
eighth ball bearing 270.
[0041] The eighth ball bearing 270 is closer to the second input
end 254 than the fifth roller bearing 258. Further, the eighth ball
bearing 270 is fixed to the stationary member 28 along the first
axial direction X1, the second axial direction X2, and the radial
direction R. Accordingly, the eighth ball bearing 270 remains
constrained or substantially stationary relative to the stationary
member 28 along the first axial direction X1, the second axial
direction X2, and the radial direction R. To do so, the
electro-mechanical drive system 216 may include a sock nut 272 (or
any other suitable fastener) coupling the eighth ball bearing 270
to the stationary member 28.
[0042] While the best modes for carrying out the invention have
been described in detail, those familiar with the art to which this
invention relates will recognize various alternative designs and
embodiments for practicing the invention within the scope of the
appended claims.
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